The Senators received center Chris Tierney and defenseman Dylan DeMelo, prospects Josh Norris and Rudolfs Balcers, a conditional 2019 second-round draft pick and a conditional 2020 first-round pick for their captain. If San Jose re-signs Karlsson, who is entering the final year of a seven-year, $45 million contract, Ottawa receives a conditional 2021 second-round selection. The Sharks also get forward Francis Perron.

“It’s extremely rare that players of this caliber become available,” Sharks general manager Doug Wilson said in a statement. “The word ‘elite’ is often thrown around casually, but Erik’s skill set and abilities fit that description like few other players in today’s game. With Erik, Brent Burns and Marc-Edouard Vlasic, we feel we have three of the NHL’s top defensemen and stand as a better team today than we were yesterday. We are thrilled to welcome Erik and his wife, Melinda, to San Jose.”

The Senators said they had offered Karlsson, a two-time Norris Trophy winner, an extension, but the sides could not come to agreement. Rumors started to build leading up to Thursday’s first day of training camp, and the Sharks, Golden Knights and Stars were mentioned as possible destinations for Karlsson.

On Monday, team owner Eugene Melnyk, chief operating officer Nic Ruszkowski and general manager Pierre Dorion took the unusual step of describing their rebuilding philosophy to the Ottawa Citizen.

“When we build our team, the direction we’re trying to go to is younger, faster and stronger,” Dorion told the newspaper. “That’s the direction of the NHL, and that’s where we need to get, too. We need to implement our younger kids as early as this year as part of the rebuild.”

Dorion admitted that the Senators’ locker room “was broken” last season. The girlfriend of forward Mike Hoffman was accused of harassing Karlsson’s wife on social media. Hoffman denied the allegations, but he was still traded away this summer.

The Senators have gone from the penthouse to the basement in a very short period of time. They came within one overtime goal of the Stanley Cup Finals in 2016 but fell apart last season, finishing seventh in the Atlantic Division. There was the locker room drama, and then before Ottawa’s outdoor game in December, Melnyk even threatened to move the team.

Now they’ve dealt their franchise player. Karlsson is a five-time All-Star who has 518 points in 627 career games. He had 62 points in 71 games last season.

“This is the right moment for us to rebuild our team and shape our future with a faster, younger and more competitive team on the ice,” Senators general manager Pierre Dorion said. “We are going to build a culture of consistency which will allow this team to sustain better performance over the long term.”

The Sharks now have two of the best offensive defensemen in the league. Burns led the team in scoring last year with 67 points. Vlasic had 32 points.

The Sharks were already strong last season. They had 100 points in the regular season and made it to the second round of the playoffs before losing to the Cinderella Golden Knights in six games.

San Jose acquired forward Evander Kane at the trade deadline last season and signed him to a seven-year, $49 million extension in May.

Tierney, 23, had 17 goals and 23 assists in 82 games last season, while 24-year-old DeMelo had no goals but 20 assists in 63 games. Norris, 19, was a first-round pick (19th overall) in the 2017 draft, and the center is going into his sophomore season at Michigan. Balcers, a 21-year-old forward, played for the San Jose Barracuda of the AHL last season.

The conditional first-round pick the Senators get will be in 2019 if the Sharks miss the playoffs, or 2020 if they make the playoffs. It is not lottery-protected. The second-round selection will be the higher of the two the Sharks own in the 2019 draft.

If Karlsson signs an extension with San Jose and the Sharks make the Stanley Cup Final in 2019, the 2021 second-round pick upgrades to a first-round selection. If Karlsson ends up on an Eastern Conference roster this season, the Senators will receive another first-round draft pick no later than 2022.